1. Field of the Invention
This invention relates to an ink-jet recording process carried out using a liquid formulation and an ink (color ink) in combination. More particularly, it relates to an ink-jet recording process carried out using a liquid formulation and an ink (color ink) in combination by applying the liquid formulation and the ink (color ink) together to a recording medium (e.g., plain paper) to form a color image that is less causative of the phenomenon of color bleeding and has water fastness.
2. Related Background Art
Ink-jet recording is a process of making a record by ejecting minute droplets of ink and adhering the ink to a recording medium such as paper. In particular, an ink-jet recording process of the type as disclosed in Japanese Patent Publication No. 61-59911, No. 61-59912 and No. 61-59914, i.e., of the type in which a heat energy is imparted to ink by using an electrothermal transducer as an ejection energy feeding means to cause the ink to bubble to eject droplets, enables easy materialization of high-density multi-orifice recording head, and hence images with a high resolution and a high quality level can be recorded at a high speed.
However, inks used in conventional ink-jet recording are commonly mainly composed of water and to which water-soluble high-boiling solvents such as glycol are added for the purposes of, e.g., preventing inks from drying and preventing orifices from clogging. When a record is made on a recording medium using such ink, problems have occurred such that no sufficient fixing performance may be attained, or uneven images may occur which are presumed to be due to uneven distribution of fillers and sizing agents on the surface of the recording medium. Especially when color images are to be obtained, a plurality of color inks are successively superimposed on the recording medium before inks with certain colors become fixed thereon, and hence there has been a problem that colors may blur or unevenly mix at boundaries between images with different colors (this phenomenon is hereinafter called "bleeding ") to make it difficult to obtain satisfactory images.
As a means for improving fixing performance to cope with such problems, Japanese Patent Application Laid-open No. 55-65269 discloses a method in which a compound capable of increasing its permeation, such as a surface active agent, is added in ink. Japanese Patent Application Laid-open No. 55-66976 also discloses use of an ink mainly composed of a volatile solvent. In the former method, in which a surface active agent is added in ink, fixing performance and bleeding can be improved and prevented to a certain extent as a result of the increase in ink permeation into the recording medium. However, coloring materials in the ink also permeate into the recording paper to a great depth to cause difficulties such as a decrease in image optical density and a lowering of chroma. In addition, it also cause a spread of ink in the lateral direction, which consequently may also cause the problems of a decrease in edge sharpness of dots and a lowering of resolution. As for the latter method, in which an ink mainly composed of a volatile solvent is used, not only the difficulties occurring in the former method may occur, but also clogging due to evaporation of solvents undesirably tends to occur at nozzles of the recording head, undesirably.
To overcome such problems, methods are also proposed in which a liquid that enables formation of good images is previously applied to the recording medium before ink is ejected. For example, Japanese Patent Application Laid-open No. 58-128862 discloses an apparatus in which a liquid that can improve ink fixing performance is superimposingly applied to ink recording positions by the use of a recording head different from ink ejecting heads. Japanese Patent Application Laid-open No. 63-60783 also discloses a method in which a liquid having a basic polymer is applied and thereafter an ink containing an anionic dye is applied to make a record. Japanese Patent Application Laid-open No. 63-22681 still also discloses a recording method in which a first liquid containing reactive chemical species and a liquid containing a compound capable of reacting with the reactive chemical species are mixed on a recording medium. Japanese Patent Application Laid-open No. 63-299971 further discloses a method in which a liquid containing an organic compound having at least two cationic groups per molecule are applied to the recording medium and thereafter the recording is performed using an ink containing an anionic dye. Japanese Patent Application Laid-open No. 64-9279 also discloses a method in which an acidic liquid containing succinic acid or the like is applied onto a recording medium and thereafter the recording is performed using an ink containing an anionic dye. Japanese Patent Application Laid-open No. 64-63185 still also discloses a method in which a liquid containing a cationic polymer and capable of making dyes insoluble by aggregation is imparted to the recording medium before the ink is imparted thereto.
Meanwhile, as means for making images highly minute, various methods have been proposed. With an improvement in resolution of ink-jet recording, a method is becoming prevailing in which ink ejection volume per dot of a recording head is made smaller than ever. For example, as regards the resolution, the pursuit thereof advances from 300 dpi and 360 dpi toward 600 dpi, 720 dpi and much higher resolution. Concurrently with this, as regards the ink ejection volume per dot, the pursuit of recording heads continues toward 40 pl, 25 pl and much smaller ejection volume.
Under such circumstances, also in plain-paper color recording techniques in which as previously stated a liquid formulation different from ink is imparted to ink recording positions by the use of an ink-jet recording head so that various performances of ink-jet recorded images on the recording medium can be improved, it is sought to more improve the reliability of liquid formulations for aggregating the dyes or pigments in inks, the reliability including not only frequency characteristics, ejection stability and durability, but also the properties of hardly causing clogging (in the present invention, hereinafter called "anti-sticking performance ") and ejection stability required after a pause of recording for a certain period of time (in the present invention, called "start-up performance ").
However, when any component, e.g., the cationic polymer, used in the liquid formulation for aggregating the dyes or pigments in inks as disclosed in the prior art is applied in the recording head for highly minute recording as stated above, having a small ink ejection volume per dot, e.g., having 2 to 25 pl ink ejection volume per dot, it has been difficult to satisfy the reliability of the liquid formulations, such as frequency characteristics, ejection stability, durability, anti-sticking performance and start-up performance.